Human Agency and Exotic Birds in New Zealand

The subject of biological invasion is now accepted as a major theme in environmental history. This paper analyses the role of human agency in the deliberately managed invasion of British birds to New Zealand in the late nineteenth century, and finds both historical and ecological relevance in the available data. Evidence concerning these introductions, largely undertaken by acclimatisation societies, has already played a significant role in the development of biological invasion theory. Analysis of some of the data has been used by ecologists to confirm the importance of propagule pressure (introduction effort) in successful introduction. This paper exploits the recently increased accessibility of historic newspaper references to acclimatisation in New Zealand and stresses their importance. Firstly, they show the limits of the database used until now by ecologists when analysing the introductions. Secondly, a close case study sheds new light on the full potential for human agency with regard to introduction effort. The historic role of skilled individuals in perfecting and passing on management techniques, increasing acclimatisation success, is explored. Attention is also given to secondary, and even tertiary, releases of exotic birds from locally-established populations within New Zealand, accelerating the rate of spread. This indicates more active, multi-layered human involvement than that identified by ecologists in their numerical analyses. Finally, it is suggested that examination of historic New Zealand avian introductions may have relevance for present-day conservation biology, given the parallel between small exotic populations seeking to establish in a new location and small populations of endangered native species trying to avoid extinction. By 1900 there may already have been a transfer of technical expertise, gained from acclimatising exotics, to the newer task of conserving the indigenous.